The present invention relates to a stereoscopic map display method, and especially to a stereoscopic map display used in a navigation system which displays roads or buildings around the car with the navigation system, or which displays an intersection by use of a perspective view from a predetermined angle with respect to the ground surface.
One of the known navigation systems, for example, a system disclosed in Japanese Patent Application Laid-Open Hei 8-292715, makes the use of a car more convenient by reading out digital map data stored in a storage medium such as a CD-ROM, a DVD, etc., and displaying buildings and roads onto a map shown on a screen, along with the directions from the current position of the car, which is determined using a position detector such as a GPS, to the target location.
In recent map data, a city-area map is stored, and detailed information such as shapes, locations, the number of floors, and so on of houses and buildings can be displayed with the city-area map. Moreover, as disclosed in Japanese Patent Application Laid-Open Hei 9-281890, some of the known navigation systems use a display method that stereoscopically displays landmark-buildings along the driving path of a car on the city map in order to intelligibly indicate a view around the car, the target location, etc., along with the views around intersections on the driving path of the car.
If map elements such as buildings are stereoscopically displayed, since a number of polygons expressing sides of the stereoscopically displayed map elements are necessary according to the number of the displayed map elements, the number of the necessary polygons is larger than that used in conventionally displaying the map elements in a plane.
Thus, if the amount of information to be displayed is increased by stereoscopically displaying map elements, a user must quickly find out the information necessary for the navigation of his car from a lot more displayed information. That is, simple stereoscopic displays of map elements do not always improve the intelligibility of the navigation guidance (hereafter referred to as the guiding ability) performed by a navigation system, but rather some stereoscopic displaying methods actually deteriorate the guiding ability.
Further, the increase in the number of polygons increases the image-deploying load on the navigation system.
An object of the present invention is to provide a means which is capable of improving the visibility of a displayed map, and/or reducing the image-displaying load by suppressing the increase in the amount of displayed information due to the stereoscopic displaying of map elements using a stereoscopic map display method, and a navigation system using the method, in which a stereoscopic scene viewed from a predetermined view point is displayed.
The above object of the present invention is attained by providing a representation method-changing means for changing a representation method for at least one of a specified group in the map elements and a map element possessing specified attributions.
In more detail describing, the present invention provides a stereoscopic map-display method of displaying a scene on a display screen corresponding to a perspective map generated by viewing the map elements in a displayed area, which is set based on the position of the moving body or the position designated by the user, from a predetermined view point, map information on the map element in the displayed area being read out of a map database, the stereoscopic map-display method comprising the step of changing a representation method for the map elements based on at least one of a distance in a straight line, a horizontal distance, and a level difference between the view point and each map element, and further provides a navigation apparatus for generating a map-image, using the method.
Here, in the above step of changing a representation method for map elements, (a) ones in the map elements, at least one of a distance in a straight line, a horizontal distance, and a level difference between each of the ones and the view point being larger than a predetermined value, (b) ones in the map elements, at least one of a distance in a straight line, a horizontal distance, and a level distance between each of the ones and the view point being smaller than a predetermined value, or (c) ones in the map elements, which are located between the view point and a position to be noticed, the position being set in the displayed area, are displayed using a representation method with lower visibility or lower drawing-detail degree than that used when displaying the rest ones in the map element.
Further, in the above step of changing a representation method for map elements, a representation method for the map element is changed based on at least one of height of the view point, a distance in a straight line, a horizontal distance, and a level distance between each of the ones and the visual. When changing the representation method, (a) map elements, the distance or level difference between the view point and each of the map elements being larger than a predetermined value under the condition that the height of the view point is higher than another predetermined value, (b) map elements, the distance or level difference between the view point and each of the map elements being smaller than a predetermined value under the condition that the height of the view point is higher than another predetermined value, or (c) map elements located between the view point and a position to be noticed, are displayed using a representation method with lower visibility or lower drawing-detail degree than that used when displaying the rest ones in the map element.
Furthermore, to attain the above object, the present invention provides a stereoscopic map-display method comprising the step of changing a representation method for each of the map elements based on attributions (the number of floors or the height of the building, the bottom area of the building, the type of the store, etc.) of the map element, the attributions being included in the map information, and further provides a navigation apparatus for generating a map-image, using the method.
For example, if the attributions include at least one of the number of floors, height, and a bottom area of an architectural body corresponding to the map element, in the step of changing a representation method, (a) map elements, at least one of at least one of the number of floors, the height, and the bottom area of the architectural body being smaller than a predetermined value, are displayed using a representation method with lower visibility or lower drawing-detail degree than that used when displaying the rest ones in the map element, or (b) map elements, at least one of at least one of the number of floors, the height, and the bottom area of the architectural body being larger than a predetermined value, are displayed using a representation method with higher visibility or higher drawing-detail degree than that used when displaying the rest ones in the map element.
Moreover, it is possible that (a) ones in the map elements, which possess the attribution designated by a user or the navigation apparatus itself, are displayed using a representation method with higher visibility or higher drawing-detail degree than that used when displaying ones not-designated by the control information in the map element, or that (b) map elements in the displayed area, which are not designated by a user or the navigation apparatus itself, are displayed using a representation method with lower visibility or lower drawing-detail degree than that used when displaying ones designated by the control information in the map element.
Still further, in the above step of changing a representation method, it is possible that a representation method for the map element is changed based on the attributions and the height of the view point. When changing the representation method, a representation method for the following map elements is changed: that is, (a) map elements whose the number of floors or the height, or the bottom area is smaller than a predetermined value under the conditions that the height of the view point is higher than a predetermined value, (b) map elements whose the number of floors or the height, or the bottom area is larger than a predetermined value under the conditions that the height of the view point is higher than a predetermined value, (c) (d) map elements not possessing attributes designated by a user or not corresponding to ones to be noticed for guidance under the conditions that the height of the view point is higher than a predetermined value, (e) map elements possessing attributes designated by a user or corresponding to ones to be noticed for guidance under the conditions that the height of the view point is lower than a predetermined value, or (f) map elements possessing attributes designated by a user or corresponding to ones to be noticed for guidance under the conditions that the height of the view point is lower than a predetermined value.
Furthermore, in the above step of changing a representation method, it is possible to change a representation method for map elements facing the road on which the moving body moves, or map elements located within a predetermined distance from the road.
Also, in the above step of changing a representation method, it is possible to change a representation method for map elements located within a predetermined distance from a target architectural body when the moving body comes within another predetermined distance from the target architectural body.
Further, the above object of the present invention can be attained by using a map-display apparatus for generating and displaying map image data with the above map-display method according to the present invention, or by a storage medium which stores a program for executing the above map display method according to the present invention in a computer.
Furthermore, the above object of the present invention can be attained with an apparatus for generating image data using the above map-display method according to the present invention, or with an apparatus for displaying a map based on the image data.